I use a forced air system - it works great. I have mine set up on a single 3/4" nipple. When I had it attached to a side nipple - there was definitely an uneven burn. The burn was from the side of the nipple to the other side of the uds. That said, the slow rate of the burn and distance from the burn to the food naturally minimizes the hot spot. When I rebuilt, I put the nipple in the center of the bottom and have a diffuser that pushes the air fairly evenly to the edges of the drum. This results in a very even burn.
I do not know how the bge door looks, but if I wagered a guess it has a plate on it to diffuse the incoming air (as apposed to simply blowing it as a single stream into the coals). My first attempt did not even have that - so anything is better than nothing and could very well be enough to give you good results.